Legal claims defining the scope of protection, as filed with the USPTO.
1. In a packet switch, as apparatus for selective header field replacement comprising: an input port process (IPP) coupled to receive an input packet comprising a header, data and cyclic redundancy code (CRC), the IPP further comprising a buffer configured to temporarily store the input packet; a database configured to store information regarding packets and routes; a search engine coupled between the IPP and the database, the search engine coupled to receive the header and configured to search the database to determine information regarding a type of the input packet; the IPP further configured to output the input packet from the buffer and to selectively replace at least one field in the header in response to the information provided by the search engine and selectively output control field information to indicate the need for additional modification of the modified input packet prior to output from the packet switch; an output port process (OPP) configured to receive the selectively modified input packet and the control field information from the IPP, the OPP configured to selectively generate at least one control signal to indicate that the modified input packet is to be further modified prior to output from the packet switch and to output the selectively modified input packet; and an output interface, the output interface coupled to the OPP to receive the at least one control signal and the selectively modified input packet, the output interface configured to output a packet from the packet switch that corresponds to the selectively modified input packet by selectively modifying, in response to the at least one control signal, at least one header field and the CRC prior to transmission of the output packet.
2. The apparatus as set forth in claim 1, wherein the type comprises an indication of whether the input packet is to be routed, wherein if the input packet is to be routed, the search engine is configured to notify the IPP that the input packet is to be routed and the destination address (DA) of a next hop.
3. The apparatus as set forth in claim 2, wherein the IPP is configured to replace a DA field of the header with a DA provided by the search engine if the search engine notifies the IPP that the input packet is to be routed.
4. The apparatus as set forth in claim 2, wherein, the control field information comprises a field set by the IPP to indicate that the source address field of the header is to be replaced prior to output of the modified input packet, the field set when the input packet is to be routed.
5. The apparatus as set forth in claim 2, wherein the at least one control signal comprises control signals to selectively indicate generation of a CRC and a replacement of a source address.
6. The apparatus as set forth in claim 5, wherein the output interface is configured to insert the address of the output interface in a source address field of the header in response to the receipt of the at least one control signal indicating replacement of the source address, and to generate a CRC in response to the at least one control signal indicating regeneration of the CRC.
7. The apparatus as set forth in claim 1, wherein the header comprises a time to live (TTL) field, the IPP further configured to decrement a value in the TTL field by one prior to output.
8. The apparatus as set forth in claim 1, wherein the header comprises a checksum field, the IPP further configured to update a value in the checksum field prior to output.
9. The apparatus as set forth in claim 2, wherein the destination address is replaced when the packet is a unicast packet.
10. The apparatus as set forth in claim 5, wherein the OPP is further configured to strip off the CRC during transmission of the modified input packet to the output interface if the output interface is to generate the CRC.
11. The apparatus as set forth in claim 1, wherein the output interface is a MAC.
12. The apparatus as set forth in claim 11, wherein the at least one control signal comprises a replace.sub.-- sa signal.
13. The apparatus as set forth in claim 11, wherein the at least one control signal comprises a state of a NO.sub.-- CRC bit in a control word transmitted to the MAC by the OPP.
14. The apparatus as set forth in claim 1, wherein the switch supports virtual local area networks (VLANs) and the type comprises an indication of whether the input packet is untagged, tagged with a valid tag or tagged with an invalid tag, where: if the input is untagged, and the search engine is configured to determine that the input packet belongs to a VLAN that has been defined, and to notify the IPP of a VLAN tag of the defined VLAN and at least one indicating that the VLAN tag is to be inserted into a VLAN tag filed of the header; if the input packet is tagged with an invalid tag, and the search engine is configured to determine that the input packet to a VLAN that has been defined, and to notify the IPP of the VLAN tag of the defined VLAN and at least one indicator indicating that the VLAN tag is to be replaced; if the input packet is tagged with an valid tag, and the search engine is configured to determine that the input packet should be routed to a different VLAN, and to notify the IPP of the VLAN tag of the different VLAN and at least one indicator indicating that the VLAN tag is to be replaced; and notherwise the search engine is configured to notify the IPP of at least one indicator that indicates no insertion or replacement of the VLAN tag.
15. The apparatus as set forth in claim 14, wherein: if the VLAN tag is to be inserted, the IPP is configured to insert the VLAN tag provided by the search engine, and generate control field information of a first state; if the VLAN tag is to be replaced, the IPP is configured to replace the VLAN tag in the input packet header with the VLAN tag provided by the search engine and generate control field information of a second state; otherwise, the IPP is configured to generate control field information of a third state.
16. The apparatus as set forth in claim 15, wherein the OPP is further configured to selectively remove the VLAN tag field in the modified input packet based on the state of the control field information.
17. The apparatus as set forth in claim 15, wherein the OPP is configured to selectively generate a control signal to regenerate a CRC based on the state of the control field information.
18. The apparatus as set forth in claim 17, wherein the output interface is configured to generate a CRC in response to the at least one control signal indicating regeneration of the CRC.
19. The apparatus as set forth in claim 1, further comprising a packet memory configured to store a selectively modified input packet received from the IPP, the packet memory further configured to store control field information, the OPP coupled to the packet memory and configured to receive the selectively modified input packet and the control field information from the packet memory.
20. A method for selectively performing header field replacement in a network switch device comprising the steps of: an input port process (IPP) buffering an input packet and providing a copy of a header associated with the input packet to a search engine; the search engine searching a database to determine a type of the input packet and notifying the IPP of the type of the input packet; the IPP selectively replacing at least one field in the header in response to the information provided by the search engine and selectively outputting control field information to indicate the need for additional modification of the modified input packet prior to output from the network switch; an output port process (OPP) reading the modified input packet and corresponding control field information from the IPP, the OPP stripping a cyclic redundancy code (CRC) associated with the input packet and selectively generating at least one control signal to an output interface to indicate that the modified input packet is to be further modified prior to output from the network switch and to output the selectively modified input packet; the output interface outputting the modified input packet further selectively modified in response to the at least one control signal received from the OPP by selectively modifying at least one header field and regenerating the CRC based upon the modified input packet.
21. The method as set forth in claim 20, further comprising the step of storing the modified input packet and control field information in a packet memory; the OPP further reading the modified input packet and control field information from the packet memory.
22. The method as set forth in claim 20, wherein the type comprises an indication of whether the input packet is to be routed, wherein if the input packet is to be routed, the search engine notifying the IPP that the input packet is to be routed and the destination address (DA) of a next hop.
23. The method as set forth in claim 22, wherein the step of the IPP selectively replacing comprises the step of replacing a DA field of the header with a DA provided by the search engine if the input packet is to be routed.
24. The method as set forth in claim 22, wherein, the control field information comprises a field (replace.sub.-- SA) set by the IPP to indicate that the source address field of the header is to be replaced prior to output of the modified input packet, the replace.sub.-- SA set when the input packet is to be routed.
25. The method as set forth in claim 22, wherein the step of generating at least one control signal comprises the step of generating control signals to selectively indicate generation of a CRC and a replacement of a source address.
26. The method as set forth in claim 25, wherein the step of outputting comprises the steps of: inserting the address of the output interface in the source address field of the header in response to the receipt of the at least one control signal indicating replacement of the source address; and generating a CRC in response to the at least one control signal indicating regeneration of the CRC.
27. The method as set forth in claim 20, wherein the switch supports virtual local area networks (VLANs) and the type comprises an indication of whether the input packet untagged, tagged with a valid tag or tagged with an invalid tag, wherein: if the input packet is untagged, and the search engine determines that the input packet belongs to a VLAN that has been defined, the search engine notifying the IPP of a VLAN tag of the defined VLAN, and further issuing at least one indicator indicating that the VLAN tag is to be inserted into a VLAN tag field of the header; if the input packet is tagged with an invalid tag, and the search engine determines that the input packet belongs to a VLAN that has been defined, the search engine notifying the IPP of the VLAN tag of the defined VLAN, and further issuing at least one indicator indicating that the VLAN tag is to be replaced; if the input packet is tagged with an valid tag, and the search engine determines that the input packet should be routed to a different VLAN, the search engine notifying the IPP of the VLAN tag of the different VLAN, and issuing at least one indicator indicating that the VLAN tag is to be replaced; and otherwise the search engine notifying the IPP of at least one indicator that indicates no insertion or replacement of the VLAN tag.
28. The method as set forth in claim 27, wherein: if the VLAN tag is to be inserted, the step of the IPP selectively replacing comprising the step of inserting the VLAN tag provided by the search engine, and the step of selectively outputting control field information comprising the step of generating control field information of a first state; if the VLAN tag is to be replaced, the step of the IPP selectively replacing comprising the step of replacing the VLAN tag in the input packet header with the VLAN tag provided by the search engine and the step of selectively outputting control field information comprising the step of generating control field information of a second state; otherwise, the step of selectively outputting control field information comprising the step of generating control field information of a third state.
29. The method as set forth in claim 28, further comprising the step of the OPP selectively removing the VLAN tag field in the modified input packet based on the state of the control field information.
30. The method as set forth in claim 28, wherein the step of selectively generating at least one control signal comprises a control signal to regenerate a CRC based on the state of the control field information.
31. The method as set forth in claim 30, wherein the output interface further selectively modifies the modified input packet by generating a CRC in response to the at least one control signal indicating regeneration of the CRC.
32. In a packet switch, an apparatus for selective header field replacement comprising: a switch element including an input port process (IPP), a database, a search engine, an output port process (OPP), and a media access controller (MAC), the IPP coupled to the MAC and the search engine the IPP receiving from the MAC header information associated with an input packet comprising a header, data and a cyclic redundancy code (CRC), the database configured to store information to facilitate forwarding and filtering of packets, the search engine coupled to the database and coupled to receive a copy of the header from the IPP, the search engine configured to search the database to determine and supply information regarding a type of the input packet and information regarding the input packet'next hop to the IPP which is configured to selectively replace at least one field in the header responsive to the type and to selectively output control field information to the OPP to indicate the need for additional modification of the input packet prior to output from the packet switch; if the type determined by the search engine indicates that the header does not change, the input packet is output from the packet switch without modification thereby preserving end-to-end error robustness; if the information determined by the search engine indicates that at least one portion of the header changes, the header of the input packet is updated by the IPP, the CRC is stripped by the OPP and regenerated by the MAC based upon the updated packet and the updated packet is output from the packet switch.
33. In a packet switch, an apparatus for selective header field replacement comprising: an input port process (IPP) configured to receive a packet comprising a header, data and cyclic redundancy code (CRC) and configured to selectively replace at least one field in the header in response to information regarding a type of packet and selectively output control field information to indicate additional modification of the packet prior to output from the switch; an output port process (OPP), coupled to the IPP, configured to receive the packet and the control field information, the OPP configured to selectively generate at least one control signal to indicate that the packet is to be further modified prior to output from the switch and to output the packet; and a media access controller (MAC) coupled to receive the at least one control signal and the packet, the MAC configured to transmit an output packet corresponding to the selectively modified packet, in response to the at least one control signal, the MAC further configured to selectively modify at least one header field and the CRC prior to transmission of the output packet.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
Unknown
October 3, 2000
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